Image sensor

ABSTRACT

An image sensor which relates to a technology for estimating crosstalk of each pixel is disclosed. The image sensor includes a pixel array including a plurality of unit test patterns, each of which is used to measure values of crosstalk components of a plurality of light blocking pixels generated by a single open pixel, the light blocking pixels and the single open pixel included in the unit test pattern, a storage circuit configured to store the measured values of the respective unit test patterns, a calculation circuit configured to calculate a crosstalk value about each target pixel included in the pixel array by combining the stored values, and a correction circuit configured to correct pixel data of the target pixel by reflecting the calculated crosstalk value in the pixel data.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority under 35 U.S.C. § 119 to Koreanpatent application No. 10-2019-0128950, filed on Oct. 17, 2019, thedisclosure of which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

Embodiments of the disclosed technology generally relate to an imagesensor, and more particularly to a technology for estimating andcorrecting crosstalk of each pixel.

BACKGROUND

Generally, a Complementary Metal Oxide Semiconductor (CMOS) Image Sensor(CIS) implemented by a CMOS process has been developed to have lowerpower consumption, lower costs, and smaller sizes than other competitiveproducts. Thus, CMOS image sensors (CISs) have been intensivelyresearched and have rapidly come into widespread use. Specifically, CMOSimage sensors (CISs) have been developed to have higher image qualitythan other competitive products, such that the application scope of CMOSimage sensors (CISs) has recently been extended to video applicationsthat require higher resolution and higher frame rate as compared tocompetitive products.

Differently from a solid state image pickup device, it is necessary forthe CMOS image sensor (CIS) to convert analog signals (pixel signals)generated from a pixel array into digital signals. In order to convertanalog signals into digital signals, the CMOS image sensor (CIS) hasbeen designed to include a high-resolution Analog-to-Digital Converter(ADC).

The analog-to-digital converter (ADC) may perform correlated doublesampling about an analog output voltage indicating an output signal ofthe pixel array, and may store the resultant voltage in one or more linememories. In addition, a sense amplifier may sense and amplify thedigital signal readout from the line memory through a column line togenerate an amplified digital signal.

SUMMARY

Various embodiments of the disclosed technology are directed toproviding an image sensor that substantially addresses one or moreissues due to limitations and disadvantages of the related art.

Embodiments of the disclosed technology relate to an image sensorcapable of correcting a crosstalk component of each pixel by measuringand calculating the crosstalk component of a light blocking pixel,resulting in improvement in pixel performance.

In accordance with an embodiment of the disclosed technology, an imagesensor may include a pixel array including a plurality of unit testpatterns, each of which is used to measure values of crosstalkcomponents of a plurality of light blocking pixels generated by a singleopen pixel, the light blocking pixels and the single open pixel includedin the unit test pattern, a storage circuit configured to store themeasured values of the respective unit test patterns, a calculationcircuit configured to calculate a crosstalk value about each targetpixel included in the pixel array by combining the stored values, and acorrection circuit configured to correct pixel data of the target pixelby reflecting the calculated crosstalk value in the pixel data.

It is to be understood that both the foregoing general description andthe following detailed description of the disclosed technology areillustrative and explanatory, and are intended to provide furtherdescription of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and beneficial aspects of the disclosedtechnology will become readily apparent with reference to the followingdetailed description when considered in conjunction with theaccompanying drawings.

FIG. 1 is a block diagram illustrating an image sensor according to anembodiment of the disclosed technology.

FIG. 2 is a detailed schematic diagram illustrating a data outputcircuit shown in FIG. 1 according to an embodiment of the disclosedtechnology.

FIG. 3 is a schematic view illustrating a unit test pattern of the imagesensor shown in FIG. 1 according to an embodiment of the disclosedtechnology.

FIGS. 4A to 4D are conceptual diagrams illustrating methods formeasuring a value of a crosstalk component of each pixel in the unittest pattern shown in FIG. 3 according to an embodiment of the disclosedtechnology.

FIGS. 5 and 6 are structural views illustrating the unit test patternshown in FIG. 4B according to an embodiment of the disclosed technology.

FIG. 7 is a structural view illustrating a test pattern for calculatinga crosstalk value of each pixel in the image sensor shown in FIG. 1according to an embodiment of the disclosed technology.

FIGS. 8A to 8D are conceptual diagrams illustrating methods forcalculating a crosstalk value of a target pixel in response to the testpattern shown in FIG. 7 according to an embodiment of the disclosedtechnology.

FIGS. 9 and 10 are conceptual diagrams illustrating the position of thetest pattern shown in FIG. 7 according to an embodiment of the disclosedtechnology.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the disclosedtechnology, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are usedthroughout the drawings to refer to the same or like portions.Throughout the specification of the disclosed technology, if a certainpart is connected (or coupled) to another part, the term “connection orcoupling” means that the certain part is directly connected (or coupled)to another part and/or is electrically connected (or coupled) to anotherpart through the medium of a third party. Spatially relative terms, suchas “below”, “beneath,” “lower,” “above,” “upper,” and the like, may beused herein for ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thefigures. Spatially relative terms may be intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the example term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

Throughout the specification of the disclosed technology, if a certainpart includes a certain component, the term “comprising or including”means that a corresponding component may further include othercomponents unless a specific meaning opposite to the correspondingcomponent is written. As used in the specification and appended claims,the terms “a”, “an”, “one”, “the” and other similar terms include bothsingular and plural forms, unless context clearly dictates otherwise.The terms used in the present application are merely used to describespecific embodiments and are not intended to limit the disclosedtechnology. A singular expression may include a plural expression unlessstated otherwise.

FIG. 1 is a block diagram illustrating an image sensor according to anembodiment of the disclosed technology.

Referring to FIG. 1, the image sensor 10 according to the embodiment ofthe disclosed technology may include a pixel array 100, a row decodingcircuit 200, a ramp signal generator 300, an analog-to-digital converter(ADC) circuit 400, a data output circuit 500, and a controller 600.

The pixel array 100 may include a plurality of pixels arranged in amatrix including rows and columns. The pixel array 100 may convert anincident light signal into an electrical signal, and may output ananalog pixel signal OUT to the ADC circuit 400. In this case, the pixelarray 100 may be driven by various drive signals, for example, a resetsignal RX, a transmission signal TX, a selection signal SX, etc. thatare received from the row decoding circuit 200.

The row decoding circuit 200 may select a row line of the pixel array100. In other words, the row decoding circuit 200 may select at leastone pixel for each row line from among pixels contained in the pixelarray 100 according to individual row lines in response to a controlsignal CON received from the controller 600, and may control operationsof the selected pixel.

The ramp signal generator 300 may generate a ramp signal RAMP inresponse to the control signal CON received from the controller 600, andmay output the ramp signal RAMP to the ADC circuit 400.

The ADC circuit 400 may convert an analog pixel signal OUT received fromthe pixel array 100 into a digital signal. The ADC circuit 400 mayinclude a correlated double sampler (CDS) circuit (not shown). Thecorrelated double sampler (CDS) circuit may hold and sample the signalsreceived from the pixels of the pixel array 100.

The ADC circuit 400 may compare the pixel signal OUT received from thepixel array 100 with the ramp signal RAMP received from the ramp signalgenerator 300, and may thus output a result of comparison between thepixel signal OUT and the ramp signal RAMP. The ADC circuit 400 may countthe number of reference clock signals CLK received from the controller600 in response to the result of comparison between the pixel signal OUTand the ramp signal RAMP, and may output a column-based counting signalCNT.

The data output circuit 500 may latch or hold the digital signal CNTreceived from the ADC circuit 400. The data output circuit 500 may latchor hold counting information, and may sequentially output pixel dataDOUT in response to an output control signal OCON and a reference clocksignal CLK. The data output circuit 500 according to the embodiment ofthe disclosed technology may measure and calculate a value of acrosstalk component of each pixel within the pixel array 100, mayreflect the measured and calculated result in pixel data DOUT, and maythus output pixel data DOUT in which the crosstalk component value iscorrected.

The controller 600 may control the row decoding circuit 200, the rampsignal generator 300, the ADC circuit 400, and the data output circuit500. In this case, the controller 600 may include a timing generator.That is, the controller 600 may control overall procedures ranging froma process of sensing image data to a process of outputting the sensedimage data according to a lapse of time.

For this purpose, the controller 600 may generate a control signal CON,and may output the control signal CON to the row decoding circuit 200and the ramp signal generator 300. The controller 600 may generate areference clock signal CLK, and may output the reference clock signalCLK to the ADC circuit 400. In addition, the controller 600 may generatean output control signal OCON, a reference clock signal CLK, and asensing enable signal SEN, and may output the output control signalOCON, the reference clock signal CLK, and the sensing enable signal SENto the data output circuit 500.

FIG. 2 is a detailed schematic diagram illustrating the data outputcircuit 500 shown in FIG. 1. The data output circuit 500 shown in FIG. 2will hereinafter be described centering upon some functions formeasuring and calculating the value of a crosstalk component from amonga plurality of functions of the data output circuit 500.

Referring to FIG. 2, the data output circuit 500 may include a storagecircuit 510, a calculation circuit 520, and a correction circuit 530.

In this case, the storage circuit 510 may receive the digital signal CNTfrom the ADC circuit 400, and may store the received digital signal CNTin a unit of a line. The storage circuit 510 may output data in a unitof a column in response to the output control signal OCON received fromthe controller 600.

In the embodiment of the disclosed technology, the storage circuit 510may store the value of a crosstalk component of each pixel that ismeasured in each unit test pattern (e.g., a unit test pattern of FIG. 3to be described below).

In the embodiment of the disclosed technology, although the storagecircuit 510 may be implemented as a line memory such as a static randomaccess memory (SRAM) or a non-volatile memory such as a One-TimeProgrammable (OTP) memory, the scope or spirit of the disclosedtechnology is not limited thereto.

The calculation circuit 520 may calculate the sum of values of crosstalkcomponents stored in the storage circuit 510, and may calculatecrosstalk values of peripheral pixels affecting each target pixel. Thetarget pixel may mean a pixel being targeted for obtaining crosstalkvalues. For example, the calculation circuit 520 may calculate acrosstalk value affecting contiguous pixels of the target pixel usingthe test pattern shown in FIG. 7. The crosstalk value calculated by thecalculation circuit 520 may be used as a value for compensating forpixel data of a valid pixel region (see FIG. 9).

The correction circuit 530 may reflect the crosstalk value calculated bythe calculation circuit 520 in the pixel data DOUT of each pixel, suchthat the correction circuit 530 may output the resultant pixel data inwhich the crosstalk value is corrected. In other words, the correctioncircuit 530 may compensate for the crosstalk value for each color abouteach target pixel.

For example, the correction circuit 530 may reflect a crosstalk value ofa red pixel (hereinafter referred to as a red(R)-pixel crosstalk value)calculated by the calculation circuit 520 in R-pixel data, resulting incorrection of pixel data. The correction circuit 530 may reflect acrosstalk value of a blue pixel (hereinafter referred to as a blue(B)-pixel crosstalk value) calculated by the calculation circuit 520 inB-pixel data, resulting in correction of pixel data. The correctioncircuit 530 may reflect a crosstalk value of a green (Gr) pixel(hereinafter referred to as a green (Gr)-pixel crosstalk value)calculated by the calculation circuit 520 in Gr-pixel data, resulting incorrection of pixel data. The correction circuit 530 may reflect acrosstalk value of a green (Gb) pixel (hereinafter referred to as agreen (Gb)-pixel crosstalk value) calculated by the calculation circuit520 in Gb-pixel data, resulting in correction of pixel data.

FIG. 3 is a schematic view illustrating a unit test pattern UTP of theimage sensor shown in FIG. 1. The unit test pattern (UTP) according tothe embodiment of the disclosed technology may be included in the pixelarray 100 of FIG. 1, and the position of the unit test pattern UTP willbe described later.

Referring to FIG. 3, the unit test pattern UTP may include a pluralityof pixels 110 arranged in a matrix. A single pixel arranged in thecenter region of the plurality of pixels 110 may be an open pixel 111.The open pixel 111 may have an open region in a manner that incidentlight can penetrate the open pixel 111 to reach a light receivingelement.

In addition, each of 8 pixels (peripheral pixel) in a region Asurrounding the open pixel 111 may be a light blocking pixel 112. Thelight blocking pixel 112 may have a blocking region in a manner thatincident light cannot penetrate the light blocking pixel 112 and thuscannot reach a light receiving element.

In addition, each of 16 pixels surrounding the region A of the lightblocking pixels 112 may be a protective pixel 113. The protective pixel113 may prevent crosstalk from flowing in an undesired direction intothe light blocking pixel 112.

FIGS. 4A to 4D are conceptual diagrams illustrating methods formeasuring the value of a crosstalk component of each pixel in the unittest pattern UTP shown in FIG. 3 according to an embodiment of thedisclosed technology.

Referring to FIGS. 4A to 4D, in accordance with the embodiment of thedisclosed technology, each of four pixel patterns composed of the redpixel (R), the blue pixel (B), the green pixel (Gb), and the other greenpixel (Gr) may be implemented as an open pixel 111. In this case, theterms “Red”, “Blue”, “Green”, etc. may refer to color filtersrespectively written in the corresponding pixels.

Although four pixel patterns according to the present embodiment arecomposed of three kinds of colors, i.e., red (R), blue (B), first green(Gr), and second green (Gb), the scope or spirit of the disclosedtechnology is not limited thereto, and the four pixel patterns accordingto the present embodiment may also be implemented as other colors asnecessary. In addition, although the first green (Gr) and the secondgreen (Gb) are identical in color to each other, the first green (Gr)and the second green (Gb) may be regarded as different from each otherso as to measure the value of a crosstalk component of each pixel.

The open pixel 111 disposed in the center region of the unit testpattern UTP may not be affected by crosstalk caused by the lightblocking pixels 112. That is, the light blocking pixels 112 block alight, such that the crosstalk component may not be transferred from thelight blocking pixels 112 to the open pixel 111.

On the other hand, the light blocking pixels 112 may be affected bycrosstalk due to incident light penetrating the open pixel 111.Therefore, by measuring the crosstalk component value of each lightblocking pixel 112, it is possible to detect each of the values ofcrosstalk components caused by the open pixel 111 which affects thelight blocking pixels 112.

FIG. 4A illustrates the unit test pattern UTP having the red pixel (R)as the open pixel 111. The red pixel (R) may not be affected bycrosstalk values caused by the light blocking pixels 112. The red pixel(R) that is not affected by crosstalk may be defined as a red pixel(oR).

For example, 8 light blocking pixels 112 (i.e., blue pixel (B), greenpixel (Gb), blue pixel (B), green pixel (Gr), green pixel (Gr), bluepixel (B), green pixel (Gb), and blue pixel (B)) may be disposed in theperipheral region A of the red pixel (oR).

Therefore, the blue pixel (B) disposed at the left upper part of theopen pixel 111 may measure the value (wRtoB) of a crosstalk componentcaused by the red pixel (oR). The green pixel (Gb) disposed at an upperpart of the open pixel 111 may measure the value (wRtoGb) of a crosstalkcomponent caused by the red pixel (oR). The blue pixel (B) disposed at aright upper part of the open pixel 111 may measure the value (wRtoB) ofa crosstalk component caused by the red pixel (oR).

The green pixel (Gr) disposed at the left side of the open pixel 111 maymeasure the value (wRtoGr) of a crosstalk component caused by the redpixel (oR). The other green pixel (Gr) disposed at the right side of theopen pixel 111 may measure the value (wRtoGr) of a crosstalk componentcaused by the red pixel (oR).

In addition, the blue pixel (B) disposed at a left lower part of theopen pixel 111 may measure the value (wRtoB) of a crosstalk componentcaused by the red pixel (oR). The green pixel (Gb) located at a lowerpart of the open pixel 111 may measure the value (wRtoGb) of a crosstalkcomponent caused by the red pixel (oR). The blue pixel (B) located at aright lower part of the open pixel 111 may measure the value (wRtoB) ofa crosstalk component caused by the red pixel (oR).

FIG. 4B illustrates the unit test pattern UTP having the green pixel(Gr) as the open pixel 111. The green pixel (Gr) may not be affected bycrosstalk values caused by the light blocking pixels 112. The greenpixel (Gr) that is not affected by crosstalk may be defined as a greenpixel (oGr).

For example, 8 light blocking pixels 112 (i.e., green pixel (Gb), bluepixel (B), green pixel (Gb), red pixel (R), red pixel (R), green pixel(Gb), blue pixel (B), and green pixel (Gb)) may be disposed in theperipheral region A of the green pixel (oGr).

Therefore, the green pixel (Gb) disposed at the left upper part of theopen pixel 111 may measure the value (wGrtoGb) of a crosstalk componentcaused by the green pixel (oGr). The blue pixel (B) disposed at an upperpart of the open pixel 111 may measure the value (wGrtoB) of a crosstalkcomponent caused by the green pixel (oGr). The green pixel (Gb) disposedat a right upper part of the open pixel 111 may measure the value(wGrtoGb) of a crosstalk component caused by the green pixel (oGr).

The red pixel (R) disposed at the left side of the open pixel 111 maymeasure the value (wGrtoR) of a crosstalk component caused by the greenpixel (oGr). The other red pixel (R) disposed at the right side of theopen pixel 111 may measure the value (wGrtoR) of a crosstalk componentcaused by the green pixel (oGr).

In addition, the green pixel (Gb) disposed at a left lower part of theopen pixel 111 may measure the value (wGrtoGb) of a crosstalk componentcaused by the green pixel (oGr). The blue pixel (B) located at a lowerpart of the open pixel 111 may measure the value (wGrtoB) of a crosstalkcomponent caused by the green pixel (oGr). The green pixel (Gb) locatedat a right lower part of the open pixel 111 may measure the value(wGrtoGb) of a crosstalk component caused by the green pixel (oGr).

FIG. 4C illustrates the unit test pattern UTP having the blue pixel (B)as the open pixel 111. The blue pixel (B) may not be affected bycrosstalk values caused by the light blocking pixels 112. The blue pixel(B) that is not affected by such crosstalk may be defined as a greenpixel (oB).

For example, 8 light blocking pixels 112 (i.e., red pixel (R), greenpixel (Gr), red pixel (R), green pixel (Gb), green pixel (Gb), red pixel(R), green pixel (Gr), and red pixel (R)) may be disposed in theperipheral region A of the blue pixel (oB).

Therefore, the red pixel (R) disposed at the left upper part of the openpixel 111 may measure the value (wBtoR) of a crosstalk component causedby the blue pixel (oB). The green pixel (Gr) disposed at an upper partof the open pixel 111 may measure the value (wBtoGr) of a crosstalkcomponent caused by the blue pixel (oB). The red pixel (R) disposed at aright upper part of the open pixel 111 may measure the value (wBtoR) ofa crosstalk component caused by the blue pixel (oB).

The green pixel (Gb) disposed at the left side of the open pixel 111 maymeasure the value (wBtoGb) of a crosstalk component caused by the greenpixel (oB). The other green pixel (Gb) disposed at the right side of theopen pixel 111 may measure the value (wBtoGb) of a crosstalk componentcaused by the blue pixel (oB).

In addition, the red pixel (R) disposed at a left lower part of the openpixel 111 may measure the value (wBtoR) of a crosstalk component causedby the blue pixel (oB). The green pixel (Gr) located at a lower part ofthe open pixel 111 may measure the value (wBtoGr) of a crosstalkcomponent caused by the blue pixel (oB). The red pixel (R) located at aright lower part of the open pixel 111 may measure the value (wBtoR) ofa crosstalk component caused by the blue pixel (oB).

FIG. 4D illustrates the unit test pattern UTP having the green pixel(Gb) as the open pixel 111. The green pixel (Gb) may not be affected bycrosstalk values caused by the light blocking pixels 112. The greenpixel (Gb) that is not affected by such crosstalk may be defined as agreen pixel (oGb).

For example, 8 light blocking pixels 112 (i.e., green pixel (Gr), redpixel (R), green pixel (Gr), blue pixel (B), blue pixel (B), green pixel(Gr), red pixel (R), and green pixel (Gr)) may be disposed in theperipheral region A of the green pixel (oGb).

Therefore, the green pixel (Gr) disposed at the left upper part of theopen pixel 111 may measure the value (wGbtoGr) of a crosstalk componentcaused by the green pixel (oGb). The red pixel (R) disposed at an upperpart of the open pixel 111 may measure the value (wGbtoR) of a crosstalkcomponent caused by the green pixel (oGb). The green pixel (Gr) disposedat a right upper part of the open pixel 111 may measure the value(wGbtoGr) of a crosstalk component caused by the green pixel (oGb).

The blue pixel (B) disposed at the left side of the open pixel 111 maymeasure the value (wGbtoB) of a crosstalk component caused by the greenpixel (oGb). The other blue pixel (B) disposed at the right side of theopen pixel 111 may measure the value (wGbtoB) of a crosstalk componentcaused by the green pixel (oGb).

In addition, the green pixel (Gr) disposed at the left lower part of theopen pixel 111 may measure the value (wGbtoGr) of a crosstalk componentcaused by the green pixel (oGb). The red pixel (R) disposed at a lowerpart of the open pixel 111 may measure the value (wGbtoR) of a crosstalkcomponent caused by the green pixel (oGb). The green pixel (Gr) disposedat a right lower part of the open pixel 111 may measure the value(wGbtoGr) of a crosstalk component caused by the green pixel (oGb).

FIGS. 5 and 6 are structural views illustrating the unit test patternUTP shown in FIG. 4B. In more detail, FIGS. 5 and 6 are cross-sectionalviews illustrating the unit test pattern UTP taken along the line B-B′shown in FIG. 4B. The embodiment shown in FIG. 5 may represent a darkstate in which light does not illuminate the unit test pattern UTP, andthe embodiment of FIG. 6 may represent a white state in which lightilluminates the unit test pattern UTP.

Referring to FIG. 5, a plurality of unit pixel regions may be formedover a substrate 120 in the unit test pattern UTP. The substrate 120 mayinclude light receiving elements 121 a to 121 c respectivelycorresponding to unit pixel regions. Each of the light receivingelements 121 a to 121 c may be isolated by a device isolation film (notshown). Each of the light receiving elements 121 a to 121 c may includea photodiode PD. In this case, the photodiode PD may generatephotocharges using received light.

An interlayer insulation film 123 including a blocking layer 122 may beformed over the substrate 120. In this case, the blocking layer 122 maybe formed of a metal line for shielding incident light. In other words,the blocking layer 122 may block incident light that is received fromthe outside through the color filters 124 and 126 in a manner that theincident light cannot reach the light receiving elements 121 a and 121c.

A plurality of color filters 124 to 126 respectively corresponding tothe unit pixel regions may be formed over the interlayer insulation film123. The plurality of color filters 124 to 126 may be used to acquirecolor images. Each of the color filters 124 to 126 may be formed foreach unit pixel region, such that the color filters 124 to 126 mayisolate respective colors from the incident light.

In this case, the color filters 124 to 126 may represent differentcolors, and may include a red color filter (R), a green color filter(G), and a blue color filter (B). For example, the color filters 124 to126 may include the red color (R) filter 124, the green color (G) filter125, and the blue color (B) filter 126. Only red light from among RGBlights of incident light may penetrate the red color filter (R) 124.Only green light from among RGB lights of incident light may penetratethe green color filter (G) 125. Only blue light from among RGB lights ofincident light may penetrate the blue color filter (B) 126.

A plurality of micro-lenses 128 respectively corresponding to the lightreceiving elements 121 a to 121 c may be respectively formed over thecolor filters 124 to 126. Each of the micro-lenses 128 may collect lightinto each unit pixel region. In this case, the micro-lens may be formedin a hemispherical shape.

As can be seen from the embodiment of FIG. 5, the green color filter (G)125 may be implemented as the open pixel 111. If the green color filter(G) 125 is implemented as the open pixel 111, the blocking layer 122 maynot be formed at a lower part of the green color filter (G) 125. On theother hand, the blocking layer 122 may be formed at a lower part of thered color filter (R) 124, and the other blocking layer 122 may be formedat a lower part of the blue color filter (B) 126. In more detail, eachof the red color filter (R) 124 and the blue color filter (B) 126 mayinclude the blocking layer 122 that blocks the incident light formeasuring the values of crosstalk components caused by the lightblocking pixels 112.

Referring to FIG. 6, if the unit test pattern UTP is in a white state,each of the red color filter (R) 124, the green color filter (G) 125,and the blue color filter (B) 126 may be illuminated by light. Althoughthe pixels receive all of the red light (R), green light (G), and bluelight (B), only the value of a specific color (i.e., R value, G value,or B value) corresponding to each of the color filters 124 to 126respectively covering the pixels can be sensed.

A light transfer region will hereinafter be described with reference toFIG. 6. In more detail, light may penetrate the green color filter (G)125 serving as the open pixel 111 from among three color filters 124 to126, such that light may reach the light receiving element 121 b. Ablocking region will hereinafter be described with reference to FIG. 6.In the blocking region, the blocking layer 122 is not formed below thegreen color filter (G) 125 serving as the open pixel 111, such thatincident light may reach the light receiving element 121 b after passingthrough the interlayer insulation film 123. In contrast, lightpenetrating the red color filter (R) 124 and the blue color filter (B)126 acting as the light blocking pixels 112 from among three colorfilters 124 to 126 may be blocked by the blocking layer 122, such thatlight does not reach the light receiving elements 121 a and 121 c.

In FIG. 6, the solid line (C) illustrates that light illuminates theunit test pattern UTP in the direction of an optical axis. The diagonalline (D) illustrates that crosstalk occurs in a spatial direction at aposition between contiguous unit pixel regions. The line (E) illustratesthat crosstalk occurs in a spectral direction in which light illuminatesthe unit test pattern UTP at a vertex of the micro-lens 128. The arrow(F) illustrates that crosstalk occurs between the light receivingelements 121 a to 121 c by an electrical field. The point (G) representsa fixed pattern noise (FPN) generable between the respective pixels.

The unit pixels contained in the pixel array 100 must receive only lightcomponents of unique colors. However, the unit pixels actuallycontiguous to each other are not completely isolated from each other,such that crosstalk may unavoidably occur between the unit pixelscontiguous to each other.

Such crosstalk may transfer undesired light components to the contiguousunit pixels, thereby degrading the color discrimination power (i.e.,color resolution) of the corresponding unit pixel. Such degradation incolor resolution of the unit pixel may reduce sensitivity of the entireimage sensor, resulting in reduction in image quality. In addition,undesired noise may exist between the respective pixels, such that itbecomes difficult to distinguish between spatial crosstalk (i.e.,crosstalk generated in the diagonal direction) and spectral crosstalk(i.e., crosstalk generated in the vertical direction), and it becomesimpossible to recognize directivity of such crosstalk.

Referring to FIG. 6, only one color filter 125 may be opened, and lightpenetrating the remaining color filters 124 and 126 may be blocked bythe blocking layer 122. As a result, although light penetrating the redcolor filter (R) 124 and the blue color filter (B) 126 are blocked bythe blocking layer 122 and thus cannot reach the light receivingelements 121 a and 121 c, the value of a crosstalk component receivedfrom the color filter 125 may reach the light receiving elements 121 aand 121 c.

Crosstalk of each pixel is one of the important indexes for improvingperformance of each pixel, such that an accurate evaluation method forsuch crosstalk is needed. Therefore, the present embodiment mayimplement open pixel patterns respectively corresponding to four colorpatterns R, Gr, Gb and B. In addition, the value of a crosstalkcomponent generated when light received from only one open pixel 111 istransferred to the light blocking pixels 112 can be measured.

That is, the values of crosstalk components affecting 8 light blockingpixels 112 and caused by the single open pixel 111 can be calculated,respectively. Therefore, at least one unit pixel, the color resolutionof which is degraded by crosstalk, may be found, and characteristics ofthe found unit pixel may be improved, resulting in increased sensitivityof the entire image sensor.

FIG. 7 is a structural view illustrating a test pattern TP forcalculating a crosstalk value of each pixel in the image sensor shown inFIG. 1 according to an embodiment of the disclosed technology.

Referring to FIG. 7, the test pattern TP may include a plurality ofpixels 110 arranged in a matrix. For example, the plurality of pixels110 may include 8 pixels arranged in a row direction and 9 pixelsarranged in a column direction, such that the pixels 110 may include atotal of 72 pixels.

In order to calculate the values of crosstalk components as describedwith reference to FIGS. 4A to 4D, the four unit test patterns (UTPs)described with reference to FIGS. 4A to 4D may be combined into thesingle test pattern TP, resulting in plural patterns of pixel groups 131to 134. The plurality of pixel groups 131 to 134 may be contiguous toeach other in a horizontal direction or in a vertical direction.

The pixel group 131 may include the red pixel (R) as the open pixel 111.The pixel group 132 may include the green pixel (Gr) as the open pixel111. The pixel group 133 may include the blue pixel (B) as the openpixel 111. The pixel group 134 may include the green pixel (Gb) as theopen pixel 111.

FIGS. 8A to 8D are conceptual diagrams illustrating methods forcalculating a crosstalk value of a target pixel in response to the testpattern TP shown in FIG. 7 according to an embodiment of the disclosedtechnology.

From the viewpoint of the pixel structure of the valid pixel region, thevalues of crosstalk components generated in different directions may bethe sum of the values of crosstalk components measured in each of theunit test patterns (UTPs) shown in FIGS. 4A to 4D. Therefore, the valuesof crosstalk components measured in each test pattern TP shown in FIGS.8A to 8D may be remapped, such that the crosstalk value (Xtalk) of eachtarget pixel can be calculated based on the remapped result. In thiscase, the re-mapping may mean re-combining values of the crosstalkcomponents according to the test pattern.

Referring to FIG. 8A, the value of a crosstalk component generated inthe valid pixel region may be the sum of crosstalk components generatedin 8 pixels surrounding the red pixel (R). The crosstalk value (Xtalk@R)caused by the peripheral pixels and affecting the red pixel (R) may becalculated using the following equation 1.Xtalk@R=(wBtoR+wGbtoR+wBtoR+wGrtoR+wGrtoR+wBtoR+wGbtoR+wBtoR)·(8×dR)  [Equation1]

Referring to Equation 1, the crosstalk value (Xtalk@R) may be acquiredby calculating the sum of the values of crosstalk components caused bythe 8 contiguous pixels measured in the unit test pattern UTP shown inFIG. 4A. In order to remove the fixed pattern noise (FPN) included ineach pixel, the value (dR) of the red pixel (R) in the dark state may besubtracted from the above sum of crosstalk values as shown in FIG. 5.

Referring to FIG. 8B, the sum of the values of crosstalk componentsgenerated in the valid pixel region may be the sum of crosstalkcomponents generated in 8 pixels surrounding the green pixel (Gr). Thecrosstalk value (Xtalk@Gr) caused by the peripheral pixels surroundingthe green pixel (Gr) may be calculated using the following equation 2.Xtalk@Gr=(wGbtoGr+wBtoGr+wGbtoGr+wRtoGr+wRtoGr+wGbtoGr+wBtoGr+wGbtoGr)·(8×dGr)  [Equation2]

Referring to Equation 2, the crosstalk value (Xtalk@Gr) may be acquiredby calculating the sum of the values of crosstalk components caused bythe 8 peripheral pixels measured in the unit test pattern UTP shown inFIG. 4B. In order to remove the fixed pattern noise (FPN) included ineach pixel, the value (dGr) of the green pixel (Gr) in the dark statemay be subtracted from the above sum of crosstalk values as shown inFIG. 5.

Referring to FIG. 8C, the sum of the values of crosstalk componentsgenerated in the valid pixel region may be the sum of crosstalkcomponents generated in 8 pixels surrounding the blue pixel (B). Thecrosstalk value (Xtalk@B) caused by the peripheral pixels surroundingthe blue pixel (B) may be calculated using the following equation 3.Xtalk@B=(wRtoB+wGrtoB+wRtoB+wGbtoB+wGbtoB+wRtoB+wGrtoB+wRtoB)·(8×dB)  [Equation3]

Referring to Equation 3, the crosstalk value (Xtalk@B) may be acquiredby calculating the sum of the values of crosstalk components caused bythe 8 peripheral pixels measured in the unit test pattern UTP shown inFIG. 4C. In order to remove the fixed pattern noise (FPN) included ineach pixel, the value (dB) of the blue pixel (B) in the dark state maybe subtracted from the above sum of crosstalk values as shown in FIG. 5.

Referring to FIG. 8D, the sum of the values of crosstalk componentsgenerated in the valid pixel region may be the sum of crosstalkcomponents generated in 8 pixels surrounding the green pixel (Gb). Thecrosstalk value (Xtalk@Gb) caused by the peripheral pixels surroundingthe green pixel (Gb) may be calculated using the following equation 4.Xtalk@Gb=(wGrtoGb+wRtoGb+wGrtoGb+wBtoGb+wBtoGb+wGrtoGb+wRtoGb+wGrtoGb)·(8×dGb)  [Equation4]

Referring to Equation 4, the crosstalk value (Xtalk@Gb) may be acquiredby calculating the sum of the values of crosstalk components caused bythe 8 peripheral pixels measured in the unit test pattern UTP shown inFIG. 4D. In order to remove the fixed pattern noise (FPN) included ineach pixel, the value (dGb) of the green pixel (Gb) in the dark statemay be subtracted from the above sum of crosstalk values as shown inFIG. 5.

FIGS. 9 and 10 are conceptual diagrams illustrating the position of thetest pattern TP shown in FIG. 7 according to an embodiment of thedisclosed technology.

Referring to FIG. 9, the test pattern TP may include a plurality of testpatterns contiguous to each other, such that the plurality of testpatterns contained in the test pattern TP may be formed in a unit of aset of test patterns (hereinafter referred to as a test pattern setTPS). At least one test pattern set (TPS) may be disposed in an opendummy region located outside the valid pixel region of the pixel array100. For example, the test pattern sets (TPSs) may be respectivelydisposed at a top-center (TC) part, a top-left (TL) part, a top-right(TR) part, a center-left (CL) part, a center-right (CR) part, abottom-center (BC) part, a bottom-left (BL) part, and a bottom-right(BR) part of the valid pixel region of the pixel array 100.

Referring to FIG. 10, the plurality of test patterns (TPs) may bedisposed in the valid pixel region of the pixel array 100 and in theopen dummy region, and may also be disposed in the entire regionincluding the center region.

As is apparent from the above description, the image sensor according tothe embodiments of the disclosed technology may correctly recognizeinformation about the magnitude and directivity of a crosstalk componentof each pixel, and may improve a structural vulnerable point of thepixel based on the recognized information, resulting in improvement insystem performance.

Those skilled in the art will appreciate that the disclosed technologymay be carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thedisclosed technology. The above embodiments are therefore to beconstrued in all aspects as illustrative and not restrictive. The scopeof the disclosed technology should be determined by the appended claimsand their legal equivalents, not by the above description. Further, allchanges coming within the meaning and equivalency range of the appendedclaims are intended to be embraced therein. In addition, it is obviousto those skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the disclosed technology or included as a new claim by asubsequent amendment after the application is filed.

Although a number of illustrative embodiments consistent with thedisclosed technology have been described, it should be understood thatnumerous other modifications and embodiments can be devised by thoseskilled in the art that will fall within the spirit and scope of theprinciples of this disclosure. Particularly, numerous variations andmodifications are possible in the component parts and/or arrangementswhich are within the scope of the disclosure, the drawings and theaccompanying claims. In addition to variations and modifications in thecomponent parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. An image sensor comprising: a pixel arrayincluding a plurality of unit test patterns, each of which is used tomeasure values of crosstalk components of a plurality of light blockingpixels generated by a single open pixel, the light blocking pixels andthe single open pixel included in the unit test pattern; a storagecircuit configured to store the measured values of the respective unittest patterns; a calculation circuit configured to calculate a crosstalkvalue for each target pixel included in the pixel array by combining thestored values; and a correction circuit configured to correct pixel dataof the target pixel by reflecting the calculated crosstalk value in thepixel data, wherein a first unit test pattern among the plurality ofunit test patterns includes a first open pixel and a plurality of firstlight blocking pixels surrounding the first open pixel and a second unittest pattern among the plurality of unit test patterns includes a secondopen pixel and a plurality of second light blocking pixels surroundingthe second open pixel, wherein at least a part of the plurality of firstlight blocking pixels are disposed in a top row line and a bottom rowline which are directly adjacent to the first open pixel, and at least apart of the plurality of second light blocking pixels are disposed in atop row line and a bottom row line which are directly adjacent to thesecond open pixel, wherein the top row line and the bottom row line ofthe first open pixel, and the top row line and the bottom row line ofthe second open pixel are not contiguous within a same corresponding rowline, and wherein the first open pixel and the second open pixel aredisposed on different row lines.
 2. The image sensor according to claim1, wherein each of the plurality of unit test patterns includes: asubstrate including a plurality of unit pixel regions respectivelycorresponding to the light blocking pixels and the single open pixel; aplurality of color filters formed over the substrate and respectivelycorresponding to the unit pixel regions; and a blocking layer formedbelow the color filters respectively corresponding to the light blockingpixels, and configured to block incident light penetrating the colorfilters respectively corresponding to the light blocking pixels.
 3. Theimage sensor according to claim 2, wherein light incident upon theplurality of light blocking pixels is blocked by the blocking layer. 4.The image sensor according to claim 1, wherein the single open pixel isformed in a center region of the unit test pattern and the plurality oflight blocking pixels are disposed in a peripheral region of the singleopen pixel.
 5. The image sensor according to claim 4, wherein each ofthe unit test patterns further includes a plurality of protective pixelsdisposed in a peripheral region of the plurality of light blockingpixels.
 6. The image sensor according to claim 5, wherein the pluralityof protective pixels is disposed to surround the plurality of lightblocking pixels in a plane.
 7. The image sensor according to claim 4,wherein light incident upon the single open pixel reaches a lightreceiving element disposed under a single color filter of the singleopen pixel.
 8. The image sensor according to claim 4, wherein when lightis incident upon the single open pixel, each of the unit test patternsis used to measure a value of a crosstalk component affecting each ofthe light blocking pixels which is caused by the single open pixel. 9.The image sensor according to claim 4, wherein the single open pixels ofthe unit test patterns have different colors from one another.
 10. Theimage sensor according to claim 4, wherein the plurality of lightblocking pixels is disposed to surround the open pixel in a plane. 11.The image sensor according to claim 4, wherein the open pixel is any oneof a red pixel, a green pixel, and a blue pixel.
 12. The image sensoraccording to claim 1, wherein the plurality of unit test patterns islocated contiguous to each other to form a test pattern.
 13. The imagesensor according to claim 12, wherein the test pattern includes: a firstunit test pattern in which a pixel having a first color is implementedas the single open pixel; a second unit test pattern in which a pixelhaving a second color is implemented as the single open pixel; a thirdunit test pattern in which a pixel having a third color is implementedas the single open pixel; and a fourth unit test pattern in which apixel having a fourth color is implemented as the single open pixel. 14.The image sensor according to claim 13, wherein the first to fourthcolors are different from each other.
 15. The image sensor according toclaim 12, wherein the test pattern is formed in an open dummy regiondisposed outside a valid pixel region of the pixel array.
 16. The imagesensor according to claim 15, wherein the test pattern is disposed in atleast one of a top-center (TC) part, a top-left (TL) part, a top-right(TR) part, a center-left (CL) part, a center-right (CR) part, abottom-center (BC) part, a bottom-left (BL) part, and a bottom-right(BR) part of the valid pixel region in a plane.
 17. The image sensoraccording to claim 12, wherein the test pattern is formed in a unit of atest pattern set in which a plurality of test patterns is locatedcontiguous to each other.
 18. The image sensor according to claim 12,wherein the test pattern is formed in an entire region including acenter region of the pixel array.
 19. The image sensor according toclaim 1, wherein the calculation circuit calculates a sum of values ofcrosstalk components of a plurality of peripheral pixels located in aperipheral region surrounding the target pixel, subtracts a value of thetarget pixel in a dark state from the calculated sum, and calculates thecrosstalk value for the target pixel.
 20. The image sensor according toclaim 19, wherein the value of the target pixel in the dark state is afixed pattern noise (FPN) of the target pixel.